// Copyright 2022 jeff.li. and/or its affiliates.
/*
 * Acknowledgement: This file originates from abseil-cpp.
 * https://github.com/abseil/abseil-cpp/blob/master/absl/strings/string_view.h
 *
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
#include <tbir/runtime/container/string_view.h>

#include <algorithm>
#include <climits>
#include <cstring>
#include <ostream>

namespace tbir::runtime {

    namespace {
        void WritePadding(std::ostream &o, size_t pad) {
            char fill_buf[32];
            memset(fill_buf, o.fill(), sizeof(fill_buf));
            while (pad) {
                size_t n = std::min(pad, sizeof(fill_buf));
                o.write(fill_buf, n);
                pad -= n;
            }
        }

        class LookupTable {
        public:
            // For each character in wanted, sets the index corresponding
            // to the ASCII code of that character. This is used by
            // the find_.*_of methods below to tell whether or not a character is in
            // the lookup table in constant time.
            explicit LookupTable(string_view wanted) {
                for (char c : wanted) {
                    table_[Index(c)] = true;
                }
            }

            bool operator[](char c) const {
                return table_[Index(c)];
            }

        private:
            static unsigned char Index(char c) {
                return static_cast<unsigned char>(c);
            }

            bool table_[UCHAR_MAX + 1] = {};
        };

        // This is significantly faster for case-sensitive matches with very
        // few possible matches.  See unit test for benchmarks.
        const char *memmatch(const char *phaystack, size_t haylen, const char *pneedle, size_t neelen) {
            if (0 == neelen) {
                return phaystack;  // even if haylen is 0
            }
            if (haylen < neelen)
                return nullptr;

            const char *match;
            const char *hayend = phaystack + haylen - neelen + 1;
            // A static cast is used here to work around the fact that memchr returns
            // a void* on Posix-compliant systems and const void* on Windows.
            while ((match = static_cast<const char *>(memchr(phaystack, pneedle[0], hayend - phaystack)))) {
                if (memcmp(match, pneedle, neelen) == 0)
                    return match;
                else
                    phaystack = match + 1;
            }
            return nullptr;
        }

    }  // namespace

    std::ostream &operator<<(std::ostream &o, string_view piece) {
        std::ostream::sentry sentry(o);
        if (sentry) {
            size_t lpad = 0;
            size_t rpad = 0;
            if (static_cast<size_t>(o.width()) > piece.size()) {
                size_t pad = o.width() - piece.size();
                if ((o.flags() & o.adjustfield) == o.left) {
                    rpad = pad;
                } else {
                    lpad = pad;
                }
            }
            if (lpad)
                WritePadding(o, lpad);
            for (auto &c : piece) {
                if (c == 0) {
                    o.write("\\x00", 4);
                } else {
                    o.put(c);
                }
            }
            if (rpad)
                WritePadding(o, rpad);
            o.width(0);
        }
        return o;
    }

    string_view::size_type string_view::find(string_view s, size_type pos) const noexcept {
        if (empty() || pos > length_) {
            if (empty() && pos == 0 && s.empty())
                return 0;
            return npos;
        }
        const char *result = memmatch(ptr_ + pos, length_ - pos, s.ptr_, s.length_);
        return result ? result - ptr_ : npos;
    }

    string_view::size_type string_view::find(char c, size_type pos) const noexcept {
        if (empty() || pos >= length_) {
            return npos;
        }
        const char *result = static_cast<const char *>(memchr(ptr_ + pos, c, length_ - pos));
        return result != nullptr ? result - ptr_ : npos;
    }

    string_view::size_type string_view::rfind(string_view s, size_type pos) const noexcept {
        if (length_ < s.length_)
            return npos;
        if (s.empty())
            return std::min(length_, pos);
        const char *last = ptr_ + std::min(length_ - s.length_, pos) + s.length_;
        const char *result = std::find_end(ptr_, last, s.ptr_, s.ptr_ + s.length_);
        return result != last ? result - ptr_ : npos;
    }

// Search range is [0..pos] inclusive.  If pos == npos, search everything.
    string_view::size_type string_view::rfind(char c, size_type pos) const noexcept {
        // Note: memrchr() is not available on Windows.
        if (empty())
            return npos;
        for (size_type i = std::min(pos, length_ - 1);; --i) {
            if (ptr_[i] == c) {
                return i;
            }
            if (i == 0)
                break;
        }
        return npos;
    }

    string_view::size_type string_view::find_first_of(string_view s, size_type pos) const noexcept {
        if (empty() || s.empty()) {
            return npos;
        }
        // Avoid the cost of LookupTable() for a single-character search.
        if (s.length_ == 1)
            return find_first_of(s.ptr_[0], pos);
        LookupTable tbl(s);
        for (size_type i = pos; i < length_; ++i) {
            if (tbl[ptr_[i]]) {
                return i;
            }
        }
        return npos;
    }

    string_view::size_type string_view::find_first_not_of(string_view s, size_type pos) const noexcept {
        if (empty())
            return npos;
        // Avoid the cost of LookupTable() for a single-character search.
        if (s.length_ == 1)
            return find_first_not_of(s.ptr_[0], pos);
        LookupTable tbl(s);
        for (size_type i = pos; i < length_; ++i) {
            if (!tbl[ptr_[i]]) {
                return i;
            }
        }
        return npos;
    }

    string_view::size_type string_view::find_first_not_of(char c, size_type pos) const noexcept {
        if (empty())
            return npos;
        for (; pos < length_; ++pos) {
            if (ptr_[pos] != c) {
                return pos;
            }
        }
        return npos;
    }

    string_view::size_type string_view::find_last_of(string_view s, size_type pos) const noexcept {
        if (empty() || s.empty())
            return npos;
        // Avoid the cost of LookupTable() for a single-character search.
        if (s.length_ == 1)
            return find_last_of(s.ptr_[0], pos);
        LookupTable tbl(s);
        for (size_type i = std::min(pos, length_ - 1);; --i) {
            if (tbl[ptr_[i]]) {
                return i;
            }
            if (i == 0)
                break;
        }
        return npos;
    }

    string_view::size_type string_view::find_last_not_of(string_view s, size_type pos) const noexcept {
        if (empty())
            return npos;
        size_type i = std::min(pos, length_ - 1);
        if (s.empty())
            return i;
        // Avoid the cost of LookupTable() for a single-character search.
        if (s.length_ == 1)
            return find_last_not_of(s.ptr_[0], pos);
        LookupTable tbl(s);
        for (;; --i) {
            if (!tbl[ptr_[i]]) {
                return i;
            }
            if (i == 0)
                break;
        }
        return npos;
    }

    string_view::size_type string_view::find_last_not_of(char c, size_type pos) const noexcept {
        if (empty())
            return npos;
        size_type i = std::min(pos, length_ - 1);
        for (;; --i) {
            if (ptr_[i] != c) {
                return i;
            }
            if (i == 0)
                break;
        }
        return npos;
    }

    constexpr string_view::size_type string_view::npos;
    constexpr string_view::size_type string_view::kMaxSize;

}  // namespace tbir::runtime
